Reject undersized SyslogAppender MaxMessageLength values#657
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swebb2066 merged 1 commit intoMay 10, 2026
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The append() splitting loop computes chunk-end iterators as
start + maxMessageLength - 12 to reserve space for an "(x/y)" sequence
suffix. With maxMessageLength == 12 the chunk size is zero and the loop
never advances, growing the packets vector indefinitely. Smaller
positive values walk the iterator before msg.begin() before constructing
LogString(start, end) with start > end (undefined behaviour).
Validate the value in setMaxMessageLength so the public setter and the
setOption("MaxMessageLength", ...) configuration path both fall back to
the documented default when the configured value cannot satisfy the
suffix-reservation arithmetic.
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The append() splitting loop computes chunk-end iterators as start + maxMessageLength - 12 to reserve space for an "(x/y)" sequence suffix. With maxMessageLength == 12 the chunk size is zero and the loop never advances, growing the packets vector indefinitely. Smaller positive values walk the iterator before msg.begin() before constructing LogString(start, end) with start > end (undefined behaviour).
Validate the value in setMaxMessageLength so the public setter and the setOption("MaxMessageLength", ...) configuration path both fall back to the documented default when the configured value cannot satisfy the suffix-reservation arithmetic.
Changes
Tests Added
Added tests covering: